EFFECT OF WATER-TABLE 145 



drawn to the surface by capillary action from a depth 

 greater- than 2 or 3 feet, so that the greater part of the alkali 

 which penetrates beyond this depth never again reappears 

 at the surface unless the water-table rises to within a few 

 feet of the surface. Water movement below the top 2 or 

 3 feet is probably caused by moisture removed by the plants 

 or by the action of gravity so that it is improbable that 

 there is such movement of salts other than local diffusion 

 and movement with the gravitational, or free, water. 



Effect of Water-table. Where the drainage is poor 

 so that there is a rise of the water-table the conditions are 

 modified accordingly. With a water-table near the sur- 

 face, the soluble salts dissolved from the soil by down- 

 ward movement are held where they may be drawn by 

 capillarity to the surface and again accumulate. Head- 

 den (14) observed that the water in shallow wells rose in 

 salt content from 2871 parts per million before an irriga- 

 tion to 4444 parts per million twelve days following and 

 then gradually fell to 2590 parts per million just before the 

 next irrigation. 



He and also Mackie (24) noticed that the concentra- 

 tion of the top of the water-table was greater than the 

 lower depths and that there was a rather gradual de- 

 cline in the soluble salts in the water with depth. As 

 the water-table rises the most concentrated solutions are 

 presented for upward translocation. Headden (14) made 

 a rather detailed study of the effect of seasonal movement 

 of water-tables from which he concluded that as the water 

 fell much of the salts in the free water was retained by the 

 soil so that the free water gradually became weaker as it 

 sank and again increased as it rose. He (15) found that 

 the kind and quantity of salts in the soil solution differed 

 markedly from those found in the free ground water or 



